Conventional ten speed bicycle transmissions consist of a chain wrapped around a front double sprocket and a rear cluster containing five sprockets, a front and rear derailleurs for derailing the chain from one sprocket to another in response to a rider moving two control levers which are connected to the derailleurs. The derailleurs are made of a large number of delicate parts which need frequent maintenance and adjustment, and are easily damaged. The derailleur system is also hard to operate, it generates continuous noise and inefficiencies in certain gears due to chain's misalignment.
Due to the derailleur system deficiencies several attempts have been made in the past to introduce different systems, some of which are based on variable-sprockets. An example is found in British Pat. No. 453,712 by Neale and U.S. Pat. No. 3,938,403 by Donaldson. These and other designs while being workable lacked the degree of refinement and simplicity to be commercially successful.
An object of the present invention is to overcome these and other deficiencies of the prior art, and to provide a simple durable self-contained integral shifter which does not require additional connection or hardware attached to the bicycle's frame and which is, therefor, easy to install and economical to mass produce.